Question About bootcamp Please help

[asweare]

Hi, guys
I own on Imac 21inch
it;s 3.06Ghz Intel Core 2 Duo
with 4 gb ram

I think it's from 2009 model

anyway, I am getting black screen when I tried to boot window 7

it happens before the installation,
I tried to look up everywhere I just couldn't find an answer can anybody help me?

this is what happens,

When I turn it on,
I see a white screen, (without apple logo)
then going to black screen, (with nothing)
then just stays there,

nothing happen, I leave like that for an hour
and still nothing..

can anybody help me ?
please

thanks